Which is wiser? Fiscally cheap or more durable?

I'm an amateaur photographer and just broke my plastic mount lens on a Nikon D200. As i'm searching to find a new lens, i find two great ones! Technically, they are the same thing, but one is plastic and sells for 400 and the other is metal and sells for almost 900.Im a student, so price really matters to me, but taking into account that i'm shopping for a new lens because i just broke my plastic mount changes the matter. Do you think i should buy the metal one or be cheap?

Added (1). Mr. Gimli, To answer your question the metal mount is the AF-S DX Nikkor 18-200mm f/3.5-5.6 ED VRII and the plastic mount is the AF-S DX Nikkor 18-105mm f/3.5-5.6 ED VR
So their pretty freaking close.

I think we need more information. If the plastic lens mount broke because you were mounting and unmounting the lens all the time, then it's obvious that you really need the metal mount. If the lens broke because of a legitimate accident (the camera tumbling down the stairs, for example) and the lens stays mounted on the camera most of the time, then I would go with the cheap lens.

I doubt, however, that the $400 lens and the $900 lens are anywhere near the same thing. Please tell us exactly what the two lenses are, and we might be able to help you a little more.